A student sets up a demonstration of electromagnetic effects using a rectangular coil of wire suspended on a pivot between the opposite poles of two permanent magnets.
Initially, the coil is connected to a direct current (d.c.) power supply. When the current is switched on, the coil begins to rotate. Explain why the coil rotates.
State two changes to the apparatus or the circuit that would make the coil rotate at a higher speed.
The power supply is then disconnected, and the coil is connected to a small light-emitting diode (LED) to form a closed loop. The student manually rotates the coil. Explain why the LED lights up.